How can I improve debug information shown on SwiftData properties marked as _SwiftDataNoType?

Question

My function fetches some SwiftData records and creates others. When I inspect them in the debugger, none of their non-nil properties are shown.

Is there something I can do to enable it to display actual values for these properties?

Answer 1

I doubt you can control how the left half of the Xcode debugger displays things.

You can, however, conform the model to CustomReflectable:

@Model
class Foo: CustomReflectable {
    var x: String
    var y: String
    init(x: String, y: String) {
        self.x = x
        self.y = y
    }
    
    // put all the model's properties in the dictionary literal here.
    // you can also write a macro to generate this.
    var customMirror: Mirror {
        Mirror(self, children: [
            "x": x,
            "y": y,
        ])
    }
}

Now, you can select the variable storing your model, and click the "i" button with a circle:

and the contents of your custom mirror will be displayed on the right half.

You can also do po dump(x) in the debugger to achieve the same effect.

---

Here is a macro that generates this CustomReflectable conformance. You can attach this to your class, in addition to @Model.

// declaration
@attached(extension, conformances: CustomReflectable, names: named(customMirror))
public macro ModelMirror() = #externalMacro(module: "ImplementationModule", type: "ModelMirrorMacro")

// implementation
enum ModelMirrorMacro: ExtensionMacro {
    static func expansion(
        of node: AttributeSyntax,
        attachedTo declaration: some DeclGroupSyntax,
        providingExtensionsOf type: some TypeSyntaxProtocol,
        conformingTo protocols: [TypeSyntax], 
        in context: some MacroExpansionContext
    ) throws -> [ExtensionDeclSyntax] {
        guard let classDecl = declaration.as(ClassDeclSyntax.self) else { return [] }
        let name = classDecl.name
        let propertyNames = classDecl.memberBlock.members.compactMap {
            $0.decl.as(VariableDeclSyntax.self)?.bindings.first?.pattern.as(IdentifierPatternSyntax.self)?.identifier
        }
        let extensionDecl = try ExtensionDeclSyntax("extension \(name): CustomReflectable") {
            let kvp = DictionaryExprSyntax(contentBuilder: {
                for name in propertyNames {
                    DictionaryElementSyntax(key: StringLiteralExprSyntax(content: name.text), value: DeclReferenceExprSyntax(baseName: name))
                }
            })
            "var customMirror: Mirror { Mirror(self, children: \(kvp)) }"
        }
        return [extensionDecl]
    }
}